1. Field of the Invention
The present invention relates to a turbofan, and more particularly, the present invention relates to a turbofan which is applied to a window-type air conditioner.
2. Description of the Related Art
Generally, as shown in FIG. 1, a window-type air conditioner has a single case 10. In the case 10, there are arranged a compressor 12 for compressing refrigerant, a condenser 14 for condensing the refrigerant which is compressed by the compressor 12 and thereby decreasing the temperature of the refrigerant, and an evaporator 16 for performing a heat-exchanging function using the refrigerant which is reduced in terms of its temperature by the condenser 14.
A space which is defined in the case 10 of the window-type air conditioner is divided into an indoor part and an outdoor part by a partition panel 18.
The evaporator 16, a turbofan 20 for circulating room air through the evaporator 16, and the like are disposed in the indoor part. The compressor 12, the condenser 14, an axial-flow fan 30 for enabling the condenser 14 to conduct a condensing function using outside air, and the like are disposed in the outdoor part.
As shown in FIG. 2, the turbofan 20 is composed of a hub 201, a plurality of blades 202 which are located at a predetermined separation from the hub 201, and a shroud 203 which is attached to distal ends of the plurality of blades 202 in opposition to the hub 201.
The turbofan 20 is connected to a driving motor 19 in a state wherein it is disposed in a scroll case 22 which defines an air passage.
In the window-type air conditioner, warm air in a room passes through the evaporator 16 by the rotating action of the turbofan 20 and thereby is cooled. Thereafter, the cooled air is drawn into the scroll case 22. Then, the drawn-in air is compressed by the plurality of blades 202 and discharged out of the scroll case 22. In this way, the temperature of the air in the room is properly adjusted so as to cool the room.
At this time, the cooled air which is discharged from the scroll case 22 is not immediately re-sucked into the scroll case 22 thanks to a static pressure increase effect which is produced inside the scroll case 22 by the presence of the shroud 203, and instead, is dispersed over a remote region.
The refrigerant, which is raised in its temperature by being brought into contact with the warm air at the evaporator 16, is re-cooled, in the course of passing through the condenser 14, by the outside air which flows into the outdoor portion due to rotating action of the axial-flow fan 30, so as to be continuously circulated.
Here, air-blowing factors which determine the air-blowing characteristics of the turbofan 20 include combination factors which are created by the relationships among the respective blades 202, individual factors which are induced by the independent nature of the respective blades 202, and separate factors which are induced by other elements except the blades 202.
The combinative factors include, as shown in FIG. 3, a number of the blades 202, a ratio D1/D2 between a diameter D1 (that is, an inner diameter of the blades) of a circle which is obtained by connecting inner ends of the respective blades 202 and a diameter D2 (that is, an outer diameter of the blades) of a circle which is obtained by connecting outer ends of the respective blades 202, and a length L2 (see FIG. 4a) of a line segment (that is, a section) which connects the outer ends of two adjoining blades 202.
The individual factors include a length L1 of a line segment (that is, a chord) which connects the inner and outer ends of each blade 202 (see FIG. 4a), an entrance angle xcex21 and an exit angle xcex22 of the blade 202 (see FIG. 4b), a maximum camber position P and a maximum thickness t of the blade 202 (see FIG. 4b), and an entrance width W1 which is the inner length of the blade 202 and an exit width W2 which is the outer length of the blade 202 (see FIG. 5).
Here, the number of the blades 202 is determined depending upon the ratio between the length L1 of the chord and the length L2 of the section. The maximum camber position P designates the relative distance from a starting point of the blade 202 to a point of maximum thickness t when assuming that the length L1 of the chord is 1.
The separate factors include the inner diameter Ds of the shroud 203 as shown in FIG. 5.
In the conventional window-type air conditioner, a sirocco fan (not shown) can be used in place of the turbofan.
Because the sirocco fan has a large air-blowing rate, the size of the sirocco fan can be decreased. However, when assuming that the turbofan and the sirocco fan have the same air-blowing rate, since the sirocco fan has increased power consumption in comparison with the turbofan, the sirocco fan has the disadvantage in that its operating efficiency is degraded. As a consequence, since the turbofan has a higher operating efficiency than the sirocco fan, it is mainly used in a window-type air conditioner. On the other hand, due to the fact that the turbofan occupies an increased volume when compared to the sirocco fan having the same air-blowing rate, the turbofan adversely affects miniaturization of the air conditioner.
The conventional turbofan 20 is fabricated by a joining method or an integral forming method. In the joining method, the separately formed shroud 203 is joined to the plurality of blades 202 in a state wherein the hub 201 and the plurality of blades 202 are integrally formed with each other. In the integral forming method, by configuring the hub 201 in a manner such that the diameter of the hub 201 is less than the outer diameter D2 of the blade 202, the hub 201, the plurality of blades 202 and the shroud 203 are integrally formed one with the other.
However, the joining method encounters a problem in that, since a separate procedure for joining the shroud 203 to the blades 202 is needed, the productivity of the turbofan is reduced. Also, the integral forming method suffers from defects in that significant operating noise is produced due to the structural features of the turbofan.
Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and thus an object of the present invention is to provide a turbofan for a window-type air conditioner, which is constructed in such a way as to be fabricated by an integral forming method, whereby the productivity of the turbofan is improved and at the same time, the air-blowing efficiency of the turbofan is improved.
In order to achieve the above object, according to one aspect of the present invention, there is provided a turbofan for a window-type air conditioner, comprising: a hub; seven to eleven blades located at a predetermined separation from the hub and gradually narrowed in their width toward the hub; and a shroud attached to the blades in opposition to the hub; wherein the entire width of the turbofan is 35-45% of an outer diameter of the blades, the exit width of the turbofan is 50-60% of the entire width, the entrance width of the turbofan is 85-92% of the entire width, the hub-side inner diameter of the blades is 45-55% of the outer diameter of the blades, and the shroud-side inner diameter of the blades is 60-70% of the outer diameter of the blades.
According to another aspect of the present invention, each blade has a shroud-side inclination angle of 30-60xc2x0, an exit angle of 50-65xc2x0, a hub-side entrance angle of 15-30xc2x0, a shroud-side entrance angle of 40-55xc2x0, a maximum camber position of 0.3-0.5, and a maximum thickness of 5-8% of the hub-side chord length or 7-12% of the shroud-side chord length.
According to still another aspect of the present invention, an inner diameter of the shroud is 70-80% of the outer diameter of the blades.
According to yet still another aspect of the present invention, the hub has a diameter which is less than the outer diameter of the blades.